Rubbish clogs Perth waterways

Almost 14 tonnes of rubbish and waste was pulled from the Swan and Canning rivers last financial year according to a report which shows the ailing system's health has gone backwards.

Shopping trolleys, chairs, drums and signs were among more than 180 big items plucked from the rivers, prompting the Swan River Trust to say that waste removal was one of its major problems.

In its annual report, the trust said it was forced to remove 13,985kg of "general refuse" from the Swan and Canning rivers in the 12 months to June 30, of which 6577kg was rubbish. The amount of material taken away was less than the previous period but this was largely due to less rainfall.

Even so, trust officers were "continuing to spend considerable time" on the task.

The figures come on top of another finding in the report which shows that both rivers are failing to meet key indicators of good health.

Results from monitoring stations show dissolved oxygen levels fell well short of their benchmarks along all but one section of the system - the lower Swan-Canning.

The report also showed levels of chlorophyll-a - a green pigment that indicates algal growth - were unacceptably high everywhere, including in one part with 41 negative results compared with an acceptable limit of three.

Although the amount of phosphorus and nitrogen entering the system was deemed generally acceptable, it was the fourth consecutive year that chlorophyll levels had exceeded targets.

The trust said the chlorophyll and dissolved oxygen results were measured against "aspirational" targets and did not suggest the river system was at significant risk of ecological harm.

"It has been a hard season on our rivers, the driest on record, and the Canning in particular was adversely affected," trust chairman Jim Freemantle wrote in the report.

"Unprecedented weather conditions are posing new challenges."

Shadow environment minister Sally Talbot said it was deplorable the Swan and Canning rivers were being used as Perth's "tip".

She questioned why the State Government was not pushing for more prosecutions.

Environment Minister Bill Marmion said most refuse that entered the rivers came through Perth's drainage system rather than dumping. However, the dumping of shopping trolleys into the Swan, particularly from footbridges, was a concern.